The invention relates to turbine blade assemblies, in particular for gas turbines.
Blade locking in turbine discs must be performed to ensure blades do not become loose during engine operation. For high pressure turbine blades, locking plates have traditionally been employed to provide both security and sealing of cooling air to prevent excessive leakages, these plates being assembled using a sequential build technique. However, where blades are assembled into discs as a full engine set (e.g. where root and platform angles are different) it is not possible to fit traditional plates as the retaining grooves in the disc and blade are full rings—therefore a new method is required.
Blade locking has traditionally been achieved using locking strips to secure pairs of blades to the disc or where improved sealing is required the use of locking plates has been employed to secure blades and discs locating in circumferential grooves on the component parts.
EP 1 657 404 A1 discloses a rotor of a turboengine with turbine blades mounted to axial grooves in the rotor. The turbine blades are prevented from moving in the axial direction by locking plates. The rhomboid locking plates are inserted into a space between two grooves in the rotor and the turbine blades and then rotated so that the edges of the rhomboids engage into the grooves to secure the turbine blades.
U.S. Pat. No. 5,662,458 discloses a bladed rotor for a high pressure compressor of a gas turbine engine with retention plates. The retention plates are carried in radially inner and outer slots and prevent axial movement of the blade roots in their slots. When all the retention plates have been inserted into the loading slot, a locking member is inserted to close the gap between the two last retention plates. The locking member is placed between an adjacent pair of retention plates to prevent their circumferential movement relative to the disc. The locking member has a lower portion that corresponds in shapes with the loading slot. It is of greater axial extend than the loading slot so that it protrudes into the radial inner slot.
GB 2 258 273 A discloses a locking arrangement for the rotor blades of a gas turbine. The locking arrangement comprises a plate which extends circumferentially over the roots of several blades. The blades are trapped between retaining hooks integral with the rotor disc and the blade roots. The plates each have a reciliently mounted hook which, when in position, prevents rotation of the plate. The plate can be released by depression of the hook.
GB 905 582 A discloses a turbine blade assembly, in particular for a gas turbine, with a turbine disc and rotor blades inserted into notches of the turbine disc and locking plates that are placed inside circular grooves with rims in the turbine disc and in the rotor blades.
U.S. Pat. No. 3,656,865 A discloses a locking plate for mounting in retaining grooves in the disc whose outer flange is discontinuous as intersected by the blade slots. The locking plate has teeth on its radially outer side that allow the insertion of the locking plates after all the blades have been mounted on the disc.